Headphone or earphone devices have been used in audiometry applications for some time. One example of such a device that has been used for many years is the TDH-39 headphone of Telephonics. The TDH-39 headphone basically comprises a metal casing that is worn on the head of a user. The casing is fitted with ear cushions that support the headphone against the outer ear in an attempt to attenuate ambient noise levels during audiometric testing. While the TDH-39 headphone has been widely used and accepted in the audiometry industry, it is quite cumbersome and uncomfortable to wear for extended periods of time and the typical leak around the cushions prevents adequate attentuation of ambient noise. In addition, because the TDH-39 has ear cushions that cover the ear canal, the TDH-39 often causes a canal “collapse” problem which may distort a user's hearing and adversely affect audiometric testing results. While superficial changes have been made to the TDH-39 over the years, such as, for example, the change from a metal to a plastic cased version (i.e., the TDH-39P), none of these changes have solved the comfort and canal collapse problems.
Another example of such a device is the ER-3 earphone of Etymotic Research Inc. The ER-3 device is generally the subject of U.S. Pat. No. 4,763,753, and was introduced as an alternative to the TDH-39 for audiometric testing. The ER-3 comprises a pair of base units that each house a transducer and are each connected to an earpiece via a sound tube. The base units are worn around the neck or shoulder area while the earpieces are inserted into the ear canal of a user. The sound tubes are generally long (e.g., 10.95 inches) to enable the positioning of the transducers a sufficient distance from the ear to minimize any interference when the earphones are used, for example, with electrical response audiometry as discussed in U.S. Pat. No. 4,763,753.
While the ER-3 provides sufficient ambient noise attenuation, is more comfortable to wear over extended periods of time, and addresses the collapsed canal problem, it produces a response that is nearly identical to that produced by the THD-39 except at 6 and 8 kHz. In addition, some audiologists have claimed to have difficulty calibrating the ER-3 at 6 kHz. At 8 kHz, the response of the ER-3 is attenuated to the point that it is out of the calibration range of standard audiometers. As can be seen from the frequency response curves set forth in FIG. 1A, the ER-3 response also becomes somewhat distorted at higher frequencies (e.g., at greater than approximately 6-8 kHz).
A further example of a prior art device is the ER-4 earphone of Etymotic Research Inc. The ER-4 is generally the subject of U.S. Pat. No. 5,887,070, and was developed for hi-fidelity music listening applications. Because the ER-4 does not have enough output to meet the specifications of standard audiometers, however, it is generally not suitable for audiometric testing below approximately 2 kHz.
Further disadvantages and limitations of prior art systems with respect to audiometric testing will become apparent to one of skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.